COPY documentation with regard to references constraints

[Bruno Wolff III]

I was unable to find any documentation clarifying if using COPY to load a 
table with rows referencing others rows in the same table, whether I 
had to worry about ordering of the input.
What I found (in 17) is that even if the references constraint wasn't 
set as deferrable, I could have rows for children before their parents 
in the COPY data and things still worked.